The US intelligence community has failed to reach any firm conclusion on the exact origin of Covid-19 and is split on whether it leaked from a lab in China or emerged in nature, even though it does not believe the virus was developed as a biological weapon, according to results of a detailed review ordered by President Joe Biden.

The Director of National Intelligence in a report on Friday said SARS-CoV-2, the virus that causes Covid-19, probably emerged and infected humans through an initial small-scale exposure that occurred no later than November 2019 with the first known cluster of Covid-19 cases arising in Wuhan, China in December 2019.

However, there was no unanimity among the intelligence community (IC) on the origins of the coronavirus.

The virus was not developed as a biological weapon. Most agencies also assess with low confidence that SARS-CoV-2 probably was not genetically engineered; however, two agencies believe there was not sufficient evidence to make an assessment either way, said the unclassified version of the report.

The report did not name the intelligence agencies.

The IC also assesses that China's officials did not have foreknowledge of the virus before the initial outbreak of Covid-19 emerged, it said.

After examining all available intelligence reporting and other information, the IC remains divided on the most likely origin of Covid-19. All agencies assess that two hypotheses are plausible: natural exposure to an infected animal and a laboratory-associated incident, the report said.

Acknowledging the receipt of the report, Biden in a statement said his administration will do everything it can to trace the roots of this outbreak that has caused so much pain and death around the world so that they can take every necessary precaution to prevent it from happening again.

Critical information about the origins of this pandemic exists in China, "yet from the beginning, government officials in China have worked to prevent international investigators and members of the global public health community from accessing it", he said.

To this day, China continues to reject calls for transparency and withhold information, even as the toll of this pandemic continues to rise, Biden alleged.

A World Health Organisation (WHO) team, which visited Wuhan, the epicentre of the pandemic in central China, concluded earlier this year that the disease most likely spilled over from an animal sold at a market.

This conclusion has been rejected by some scientists.

In May, President Biden asked US intelligence agencies to assess the data and produce a report that "could bring us closer to a definitive conclusion" on the origins of the virus.

Four IC elements and the National Intelligence Council assess with low confidence that the initial SARS-CoV-2 infection was most likely caused by natural exposure to an animal infected with it or a close progenitor virus-a virus that probably would be more than 99 per cent similar to SARS-CoV-2.

These analysts give weight to Chinese officials' lack of foreknowledge, the numerous vectors for natural exposure, and other factors, the report said.

One IC element assesses with moderate confidence that the first human infection with SARS-CoV-2 most likely was the result of a laboratory-associated incident, probably involving experimentation, animal handling, or sampling by the Wuhan Institute of Virology. These analysts give weight to the inherently risky nature of work on coronaviruses, it said.

The report said the intelligence community wouldn't be able to reach a more definitive conclusion unless it receives more information.

Analysts at three IC elements remain unable to coalesce around either explanation without additional information, with some analysts favouring natural origin, others a laboratory origin, and some seeing the hypotheses as equally likely," the report said.

"Variations in analytic views largely stem from differences in how agencies weigh intelligence reporting and scientific publications, and intelligence and scientific gaps, it said.

China's foreign ministry attacked the US investigation ahead of the report's release. Fu Cong, a foreign ministry director general, said at a briefing for foreign journalists that "scapegoating China cannot whitewash the US."

According to Johns Hopkins University data, the deadly virus has so far infected 215,290,716 people and claimed 4,483,136 lives globally.

The US is the worst-hit nation with a total of 38,682,072 infections and 636,565 deaths recorded so far. The pandemic has led to a massive global economic slump, affecting the lives of millions of people.

The world deserves answers, and I will not rest until we get them. Responsible nations do not shirk these kinds of responsibilities to the rest of the world. Pandemics do not respect international borders, and we all must better understand how Covid-19 came to be to prevent further pandemics, Biden said.

America will continue working with like-minded partners around the world to press China to fully share information and to cooperate with the WHO's Phase II evidence-based, expert-led determination into the origins of CovidU-19 including by providing access to all relevant data and evidence, he said.

Biden said the US will also continue to press China to adhere to scientific norms and standards, including sharing information and data from the earliest days of the pandemic, protocols related to bio-safety, and information from animal populations.

"We must have a full and transparent accounting of this global tragedy. Nothing less is acceptable, he said.

(PTI)